There are many diseases and conditions which may require a patient to inject themselves with a drug. Accordingly, drug injection devices such as autoinjectors, injection pens, and the like, have been developed to permit a patient or user to conveniently and accurately self-administer proper doses of a drug.
In some injection devices, the injection needle may be fixed relative to the primary container, therefore, the patient or user must apply a force to pierce the skin to deliver the drug. Once the injection needle has achieved the required depth of penetration, which is typically controlled by the patient or user, a drive mechanism advances a plunger which delivers the drug contained in the primary container through the injection needle.
Since the patient or user is responsible for the penetration depth, it would be helpful to the patient or user if the drug injection device had some way of indicating to the patient or user when the correct depth has been achieved. It would also be helpful if the drug injection device could indicate to the patient or user when other stages of the injection process are occurring or have occurred and/or other information, which facilitate the convenient and accurate use of the device.